The present invention relates to systems for applying liquid compositions to the individual fibers of a fan of fibers. More particularly, the present invention relates to an apparatus for applying a liquid composition to the individual fibers of a fan of fibers, wherein the liquid composition is directed onto the fan of fibers such that a substantially uniform coating of the liquid composition is applied to each of the fibers.
Fiberglass strands used, for example, in manufacturing fiberglass-reinforced products, typically are formed by gathering the individual fibers of a fan of glass fibers exiting a glass fiber-forming bushing and by combining the individual glass fibers into one or more strands. Typically, a sizing composition is applied, such as, by an applicator roll, to the individual fibers, wherein the sizing composition serves to reduce fiber stress caused by, for example, fiber-to-fiber friction associated with direct fiber-to-fiber contact. The applicator roll typically is cylindrical, is constructed from graphite and is driven to rotate at a modest rotational velocity, relative to the tangential linear velocity of the fibers as they pass over (and typically contact) the roll.
The sizing composition is applied to the roll, such as, for example, by submerging a portion of the roll into a shallow pool of sizing composition contained within a pan. The roll is then rotated such that the sizing composition is transferred to a position of the roll, whereat the fan of fibers momentarily contact, or xe2x80x9ckissxe2x80x9d, the roll and pick up a small quantity of the sizing composition. The amount of sizing applied to the fibers by the applicator roll is controlled, for example, by controlling the rotational velocity of the roll relative to the tangential linear velocity of the fibers as they kiss the roll. U.S. Pat. No. 4,517,916 to Barch, et al. is illustrative of prior art attempts to provide a cylindrical applicator roll for applying a chemical treatment to textile fibers.
However, an applicator roll typically does not substantially uniformly coat the fibers with the sizing composition. Moreover, direct fiber-to-roll contact oftentimes results in so-called xe2x80x9cfiber walkingxe2x80x9d of the fibers over the surface of the roll, as well as increases shear and tensile stresses within the fibers. Of course, increasing the stresses within the fibers thereby increases the likelihood that the fibers may break while being gathering into a strand. More importantly, the imparted stresses may contribute to diminished performance in finished composite structures. Because conventional fiber gathering machines typically operate at high rates of speed, fiber breakage during gathering oftentimes results in significant periods of machine downtime and in the generation of excessive waste material. It is therefore desirable to provide an apparatus for applying a liquid composition to one or more fibers of a fan of fibers, wherein fiber stress is minimized.
One known method of applying a coating, for example, of fluent material, to a moving surface, such as, to a web of knitted or woven fabric, wherein it is not necessary to contact the web in order to apply the fluent material thereto, is taught by U.S. Pat. No. 5,795,391 to Niemann, et al., which provides a row of rotatable spray heads oriented transversely to a path of travel of the web. The rotatably spray heads are positioned within a shroud having an elongated opening, through which the spray heads direct a single plane-like stream of fluent material or course droplets onto the web as the web travels thereby. However, because coating efficiency typically decreases as the velocity at which the web travels past the elongated opening increases, a row of rotatable spray heads, such as is taught by Niemann ""391, is not adapted to apply a coating, for example, of a sizing composition, to a fan of fibers, for example, of fiberglass fibers, which typically travels at a high rate of speed. It is therefore desirable to provide an apparatus for applying a liquid composition to one or more fibers of a fan of fibers traveling at a high rate of speed.
It is furthermore desirable to provide an apparatus for applying a liquid composition to one or more fibers of a fan of fibers traveling at a high rate of speed, wherein a substantially uniform coating of the liquid composition is applied to each of the fibers.
It is also desirable to provide an apparatus and method for applying a liquid composition to one or more fibers of a fan of fibers traveling at a high rate of speed, wherein a substantially uniform coating of the liquid composition is applied to the fibers, and wherein the apparatus does not contact the fibers directly.
The present invention is for an apparatus and method for applying a liquid composition to one or more fibers of a fan of fibers traveling at a high rate of speed. For example, the present invention provides an apparatus and method for applying a sizing composition to one or more fiberglass fibers being gathered into one or more fiberglass strands used, for example, as reinforcing fibers of a fiberglass-reinforced product.
According to a preferred embodiment of the present invention, an apparatus for applying a liquid composition to one or more fibers of a fan of fibers traveling at a high rate of speed includes a housing (also referred to herein as an xe2x80x9cenclosurexe2x80x9d) defining an elongated passageway therethrough and a plurality of centrifugal spray heads mounted within the housing. Each of the plurality of spray heads receives liquid composition and directs atomized liquid composition into the passageway of the housing such that, as the fan of fibers travels along a path through the passageway, the fibers are coated substantially uniformly with droplets of the liquid composition.
Preferably, the plurality of spray heads include a first spray head positioned within the housing such that an atomized composition is directed therefrom towards a first location of the path, and a second spray head positioned within the housing such that an atomized liquid composition is directed therefrom towards a second location of the path. The first and second locations are spaced along the path such that atomized liquid composition is directed onto the fibers at at least two separate locations thereof, thereby increasing the overall coating efficiency of the apparatus.
In one implementation, the housing is of a substantially box-like construction surrounding the spray heads and includes an access panel removably affixed thereto for gaining access to the spray heads. A drive is mounted to the housing and is operatively connected to each of the spray heads, preferably in parallel, using timing belts or the like, to provide rotational movement of any rotational components of the spray heads. In another implementation, a shaft structure driven by an air motor or like device is provided for driving multiple spray heads in unison. The housing includes one mounting shelf for each of the spray heads. Each mounting shelf may include shields, baffles, deflectors, or the like, extending therefrom to control or direct either atomized liquid composition exiting the spray head mounted therein or air circulating within the housing. Each mounting shelf may be pivotably affixed to the housing such that the angle or orientation of the spray head mounted therein is adjustable, relative to the plane or path of travel of the fan of fibers moving through the passageway of the housing, thereby providing control of the angle at which the atomized liquid composition exiting the spray head impinges on the moving fan of fibers.
Assuming that the fan of fibers is substantially longer than it is wide, and assuming further that the fan of fibers travels along a path through the passageway, the first and second spray heads may be positioned either both facing one surface of the fan (i.e., both spray heads are on one side of the fan) or each facing an opposing surface of the fan (i.e., one spray head is on either side of the fan). Where the first and second spray heads are both positioned on the same side of the fan, a vacuum source may be connected to the housing on the other side of the fan, thereby drawing the atomized liquid composition through the fan of fibers and increasing the overall coating efficiency of the apparatus. Moreover, one or more air blast nozzles may be positioned near an outlet of the passageway to direct pressurized air thereacross, thereby reducing the amount of atomized liquid composition escaping from the housing through the outlet of the passageway.
A metering device, such as a conventional metering pump, is connected at a low pressure inlet thereof to a drain orifice in the housing and connected at a high pressure outlet thereof to a manifold supplying one or more of the spray heads with liquid composition, whereby runoff liquid composition not picked up by the fibers is re-circulated to the spray heads.
The present invention further provides a centrifugal spray head for use, preferably, with the apparatus and method according to the preferred embodiment hereof. The spray head constructed in accordance with one embodiment of the present invention includes a stator having a body defining an elongated throughbore and a substantially planar circumferential shear plate extending radially therefrom. A rotor shaft is positioned within the throughbore and includes an upper end projecting upwardly therefrom and a lower end projecting downwardly therefrom. A pulley is affixed to the upper end of the rotor shaft and is operatively connected to a drive, such as, for example, by a timing belt or the like, for rotating the rotor shaft within the throughbore. Alternatively, an air motor or like device, which may be coaxial with the rotor shaft, is coupled to the shaft to effect rotation thereof. A generally cup-shaped enclosure is affixed to the lower end of the rotor shaft and extends upwardly therefrom, terminating in a ring portion extending radially outwardly therefrom. The ring portion of the enclosure lies within a plane which is substantially parallel to, and spaced from, a plane in which the shear plate of the body lies. Rotation of the rotor shaft, then, rotates the enclosure, which rotates the ring portion thereof relative to the fixed shear plate of the body.
The rotor shaft includes an elongated passageway, which supplies liquid composition under pressure from an open upper end thereof to a liquid chamber formed between the body and the enclosure, through one or more orifices provided in the rotor shaft near the lower end thereof. Liquid composition, then, is supplied to the liquid chamber and expelled therefrom through a plurality of circumferential dispensing orifices. One or more upstanding dispensing ribs may project upwardly from an upper surface of the ring portion of the enclosure and ride against a lower surface of the shear plate. The dispensing ribs thereby define the radial orifices through which liquid sizing composition is expelled. The size, shape and layout of the orifices are provided to obtain a predetermined droplet size and density of the atomized liquid composition created thereby.